Xamarin Forms: Issue with file upload (Xamarin.Essentials) - xamarin.forms

Question

I was using Plugin.FilePicker to pick files from the device. It was working fine on android version 11 and below. But on android version 12 and above, it is breaking with below exception:
Java.Lang.NullPointerException: uri
at Java.Interop.JniEnvironment+InstanceMethods.CallNonvirtualObjectMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00088] in /Users/runner/work/1/s/xamarin-android/external/Java.Interop/src/Java.Interop/obj/Release/JniEnvironment.g.cs:11928
at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeNonvirtualObjectMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x0001e] in /Users/runner/work/1/s/xamarin-android/external/Java.Interop/src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs:894
at Android.Content.ContentResolver.Query (Android.Net.Uri uri, System.String[] projection, System.String selection, System.String[] selectionArgs, System.String sortOrder) [0x000a0] in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-33/mcw/Android.Content.ContentResolver.cs:1456
at Plugin.FilePicker.IOUtil.GetDataColumn (Android.Content.Context context, Android.Net.Uri uri, System.String selection, System.String[] selectionArgs) [0x00013] in D:\a\1\s\src\Plugin.FilePicker\Android\IOUtil.android.cs:151
at Plugin.FilePicker.IOUtil.GetPath (Android.Content.Context context, Android.Net.Uri uri) [0x00167] in D:\a\1\s\src\Plugin.FilePicker\Android\IOUtil.android.cs:108
at Plugin.FilePicker.FilePickerActivity.OnActivityResult (System.Int32 requestCode, Android.App.Result resultCode, Android.Content.Intent data) [0x00039] in D:\a\1\s\src\Plugin.FilePicker\Android\FilePickerActivity.android.cs:151
--- End of stack trace from previous location where exception was thrown ---
at Plugin.FilePicker.FilePickerImplementation.PickFile (System.String[] allowedTypes) [0x00028] in D:\a\1\s\src\Plugin.FilePicker\Android\FilePickerImplementation.android.cs:60
at CatholicBrain.ConnectAppModule.CreateActivityPage.PickFile (System.Object sender, System.EventArgs args) [0x00075] in :0
--- End of managed Java.Lang.NullPointerException stack trace ---
java.lang.NullPointerException: uri
at java.util.Objects.requireNonNull(Objects.java:245)
at android.content.ContentResolver.query(ContentResolver.java:1225)
at android.content.ContentResolver.query(ContentResolver.java:1184)
at android.content.ContentResolver.query(ContentResolver.java:1140)
at crc64424a8adc5a1fbe28.FilePickerActivity.n_onActivityResult(Native Method)
at crc64424a8adc5a1fbe28.FilePickerActivity.onActivityResult(FilePickerActivity.java:48)
at android.app.Activity.dispatchActivityResult(Activity.java:8840)
at android.app.ActivityThread.deliverResults(ActivityThread.java:5694)
at android.app.ActivityThread.handleSendResult(ActivityThread.java:5740)
at android.app.servertransaction.ActivityResultItem.execute(ActivityResultItem.java:54)
at android.app.servertransaction.ActivityTransactionItem.execute(ActivityTransactionItem.java:45)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2458)
at android.os.Handler.dispatchMessage(Handler.java:106)
at android.os.Looper.loopOnce(Looper.java:233)
at android.os.Looper.loop(Looper.java:334)
at android.app.ActivityThread.main(ActivityThread.java:8501)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:582)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
I checked for any updates for Plugin.FilePicker and found that the package is deprecated. So I installed the Xamarin.Essentials package and updated codes for picking files. It is working fine on android version 12 and above.
Xamarin.Essentials.FileResult file = null;
file = await FilePicker.PickAsync();
if (file != null)
{
filename_label.IsVisible = true;
filename_label.Text = file.FileName;
upload_layout.IsVisible = true;
}
But when I try to upload the file using our REST API it fails with below exception:
System.IO.FileNotFoundException: hail-mary.pdf
File name: 'hail-mary.pdf' ---> Java.IO.FileNotFoundException: hail-mary.pdf
at Java.Interop.JniEnvironment+InstanceMethods.CallObjectMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00068] in /Users/runner/work/1/s/xamarin-android/external/Java.Interop/src/Java.Interop/obj/Release/JniEnvironment.g.cs:11524
at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeAbstractObjectMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x0001e] in /Users/runner/work/1/s/xamarin-android/external/Java.Interop/src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs:848
at Android.Content.Res.AssetManager.Open (System.String fileName) [0x0001f] in /Users/runner/work/1/s/xamarin-android/src/Mono.Android/obj/Release/monoandroid10/android-33/mcw/Android.Content.Res.AssetManager.cs:265
at Xamarin.Essentials.FileSystem.PlatformOpenAppPackageFileAsync (System.String filename) [0x0001d] in D:\a_work\1\s\Xamarin.Essentials\FileSystem\FileSystem.android.cs:48
--- End of managed Java.IO.FileNotFoundException stack trace ---
java.io.FileNotFoundException: hail-mary.pdf
at android.content.res.AssetManager.nativeOpenAsset(Native Method)
at android.content.res.AssetManager.open(AssetManager.java:893)
at android.content.res.AssetManager.open(AssetManager.java:870)
at crc64ee486da937c010f4.ButtonRenderer.n_onClick(Native Method)
at crc64ee486da937c010f4.ButtonRenderer.onClick(ButtonRenderer.java:107)
at android.view.View.performClick(View.java:7512)
at android.view.View.performClickInternal(View.java:7489)
at android.view.View.access$3700(View.java:857)
at android.view.View$PerformClick.run(View.java:29034)
at android.os.Handler.handleCallback(Handler.java:938)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loopOnce(Looper.java:233)
at android.os.Looper.loop(Looper.java:334)
at android.app.ActivityThread.main(ActivityThread.java:8501)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:582)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1068)
at Xamarin.Essentials.FileSystem.PlatformOpenAppPackageFileAsync (System.String filename) [0x00036] in D:\a_work\1\s\Xamarin.Essentials\FileSystem\FileSystem.android.cs:52
at Xamarin.Essentials.FileSystem.OpenAppPackageFileAsync (System.String filename) [0x00000] in D:\a_work\1\s\Xamarin.Essentials\FileSystem\FileSystem.shared.cs:16
at CatholicBrain.ConnectAppModule.CreateActivityPage.UploadFile (System.Object sender, System.EventArgs e) [0x00126] in <8fb254ba200e4d369cb3f96cc3e665ff>:0
Upload Code:
var content = new MultipartFormDataContent();
Stream stream = await FileSystem.OpenAppPackageFileAsync(file.FileName);
byte[] data;
using (MemoryStream ms = new MemoryStream())
{
stream.CopyTo(ms);
data = ms.ToArray();
ms.Dispose();
}
content.Add(new StreamContent(stream), "\"fileUpload\"", $"\"{file.FullPath}\"");
var httpClient = new HttpClient();
var response = await httpClient.PostAsync(new Uri(REST API Path), content);
file.FullPath is provided on the upload code but getting FileNotFoundException.

Answer 1

If you use FilePicker.PickAsync(); to get the file, you do not need to use Stream stream = await FileSystem.OpenAppPackageFileAsync(file.FullPath); to read it to stream.
Just use Stream stream = await file.OpenReadAsync(); directly, then you can get the stream.